Apparatus for meterless exposure value indication

ABSTRACT

An exposure measuring apparatus has a lighting element which can be connected to and influenced by a source of supply potential. Means are provided for presetting the light emission of the lighting element. A photo-sensitive receiver influenced by prevailing light conditions is connectable with the source of supply potential and influences the light emission of a second lighting element which is connected in circuit with the photosensitive receiver and at least one resistance attenuation element. The resistance attenuation element or elements are adapted to adjust the light emission of the second lighting element in accordance with required exposure factors when the supply potential is connected. The lighting elements are formed as light source pillars the color of which are influenced by their supply frequency, e.g. electro luminescent plates. The source of supply potential is an alternating current source and the second lighting element is connected therewith via a variable frequency generator the frequency of which is influenced by the setting of the resistance attenuation elements. The first and second lighting elements are arranged to illuminate respective surfaces positioned immediately adjacent one another whereby when the color and brightness of each of the surfaces is equal, the exposure factors are set to values required for accurate exposure.

United States Patent Reimann et al.

154] APPARATUS FOR METERLESS EXPOSURE VALUE INDICATION [72] Inventors: Hubertus Reimann; Fritz Lindner,

both of Dresden, Germany [73] Assignee: Kombinat Veb Pentacon Dresden Kamera-und Kinowerke, Dresden, Germany [22] Filed: July 18, 1969 [21] Appl. No.: 843,148

[52] US. Cl. ..95/10 C [51] Int. Cl ..G0lj 1/10 [58] Field of Search ..95/l0 A, 10 B, 10 C; 355/68 [56] References Cited UNITED STATES PATENTS 3,332,332 7/1967 Blain ..355/69 X 3,532,035 10/1970 Fujii ..95/l0 C 3,533,705 10/1970 Fukushima ..95/10 C 1,913,719 6/1933 Nauman ..95/l0C 2,649,017 8/1953 McCarty ..95/10 B 3,094,035 6/1963 Baasner ..95/l0 C 3,323,430 6/1967 Cooper ..95/l0 B 3,323,431 6/1967 Land ..95/l0 B 3,413,066 11/1968 Biber ..95/l0 A 3,505,935 4/1970 Land ..95/l0 B FOREIGN PATENTS OR APPLICATIONS 406,475 3/1934 Great Britain ..95/l0 A 51 Oct. 17, 1972 Primary Examiner-Samuel S. Matthews Assistant Examiner-Monroe I-I. Hayes Attorney-Young & Thompson [57] ABSTRACT An exposure measuring apparatus has a lighting element which can be connected to and influenced by a source of supply potential. Means are provided for presetting the light emission of the lighting element. A photo-sensitive receiver influenced by prevailing light conditions is connectable with the source of supply potential and influences the light emission of a second lighting element which is connected in circuit with the photo-sensitive receiver and at least one resistance attenuation element. The resistance attenuation element or elements are adapted to adjust the light emission of the second lighting element in accordance with required exposure factors when the supply potential is connected. The lighting elements are formed as light source pillars the color of which are influenced by their supply frequency, e.g. electro luminescent plates. The source of supply potential is an alternating current source and the second lighting element is connected therewith via a variable frequency generator the frequency of which is influenced by the setting of the resistance attenuation elements. The first and second lighting elements are arranged to illuminate respective surfaces positioned immediately adjacent one another whereby when the color and brightness of each of the surfaces is equal, the exposure factors are set to values required for accurate exposure.

1 Claim, 7 Drawing Figures APPARATUS FOR METERLESS EXPOSURE VALUE INDICATION BACKGROUND TO THE INVENTION The invention relates to an apparatus for meterless exposure indication in photographic appliances, in which it is indicated by means of a light indicator whether the combination of exposure factors set in each case corresponds to an under-exposure, over-exl I lighting effects deriving therefrom can be evaluated for the initially described indication.

By reason of the fact that the voltage values for the lighting and extinguishing of these discharge lamps differ from one another, apart from the excessively high space requirements for these lamps, the exact setting of the correct factor combination is rendered difficult.

It is the purpose of the invention to eliminate these disadvantages.

The object of the invention consists in providing an indicator apparatus with two lighting elements which have small space and power requirements and always ensure a reliably reproducible setting of the correct exposure. Furthermore it should disclose the approximate degree of an intentional under or over exposure.

SUMMARY OF THE INVENTION According to the invention there is provided an exposure measuring apparatus including a first lighting element connectable to and influenced by a source of supply potential, means for presetting the light-emission of the lighting element connected with the lighting element, a photo-sensitive receiver influenced by prevailing light conditions connectable with said source of supply potential connected in circuit with a second lighting element and effective to control the light-emission of said second lighting element and at least one resistance attenuation element connected in circuit with the second lighting element and adapted to adjust the light emission of the second lighting element in accordance with required exposure factors when the source of supply potential is connected, wherein the lighting elements are formed as light source pillars the color of which are influenced by the frequency of their supply potential, e.g. electro luminescent plates, the source of supply potential is an alternating current source and the second lighting element is connected therewith via a variable frequency generator the frequency of which is influenced by the setting of the resistance attenuation elements, said first and second lighting elements being arranged to illuminate respective surfaces positioned immediately adjacent one another whereby when the color and brightness of each of said surfaces is equal, the exposure factors are set to values required for accurate exposure. The lighting elements can be formed as incandescent lamps which each illuminate a transparent or reflecting surface, which surfaces immediately adjoin one another to facilitate a comparison of brightness. Likewise the lighting elements can consist of luminous source pillars, for example electro-luminescent plates or the like. In this case,

apart from a monochromatic brightness comparison, a color comparison can also be carried out if one of the luminescent plates is fed with a voltage of constant frequency and the other with a voltage of a frequency variable in dependence upon the set exposure factor combination, whereby the latter plate is stimulated to emit light of different wavelengths. The correct exposure is set at color equality. The lighting surfaces screened from the external light are provided with symbols for rotation direction for the exposure setting members or they are themselves formed as such. If the apparatus according to the invention is used in a photographic camera, the lighting surfaces are visible in the viewfinder beside the picture-area limiting frame. The photoconductive cell in this case is preferably exposed to the light of the picture-taking ray path. However the apparatus is likewise usable in hand exposure meters. A strip of graduated transparency before the comparison surface serves for voltage inspection.

With the apparatus according to the invention an exact setting of the correct exposure is possible since on the one hand the mutually adjoining lighting surfaces disclose even the smallest differences of brightness or color and on the other hand a voltage variation results in a multiplied variation of the luminous flux emitted by the lighting elements. The possibility of effecting an inspection of the battery voltage completes the accuracy of adjustment.

The invention will be explained by way of example with reference to the accompanying drawings which show an embodiment of the invention incorporated in a photographic camera wherein:

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows a circuit diagram of one embodiment of the indicating apparatus,

FIGS. 2 to 5 show the formation of the surfaces to be illuminated,

FIG. 6 shows the arrangement of the lighting elements,

'FIG. 7 shows the arrangement of the lighting surfaces in the viewfinder.

DESCRIPTION OF PREFERRED EMBODIMENT According to.FIG. 1 an incandescent lamp 1 and an adjustment resistor 2 which is to be preset, is connectable through a switch 3 to a voltage source 4. An incandescent lamp 8 is connected with the voltage source 4, through a photoconductive cell 5 exposed to the light from a subject to be photographed, a resistance attenuation element 6 coupled in a manner not illustrated with the setting members for exposure time and film sensitivity of the camera and a resistance attenuator 7 coupled with the diaphragm setting member of the camera. In place of the battery 4 an alternating-current voltage source 9 can also be used and an amplifier 10 can be interposed between resistance attenuator 7 and incandescent lamp 8. Each of the incandescent lamps l, 8 is arranged behind one of the transparent surfaces l1, l2 screened from extraneous light (FIG. 6), which adjoin one another directly and are uniformly illuminated possibly in color. They are formed as or provided with symbols of direction or rotation for the setting members of the camera (FIGS. 2 to 5). A condenser lens 13 is arranged in front of the surfaces ll, 12.

The surface 12 is partially covered with a strip 14 which possesses three sections of different transparence. Between the strip 14 and the surface 12 there are opaque symbols, for example numerals, letters, etc., indicating the voltage condition of the utilized voltage source (FIGS. 2 and 7).

The manner of operation is as follows:

After the switch 3 is closed the unregulated incandescent lamp 1, which is independent of the exposure setting, emits a constant luminous flux determined by the adjusting resistance 2, with which the surface 11 is uniformly illuminated. The lamp 8 can be regulated in brightness by means of the photoconductive cell and the resistance attenuation elements 6, 7. The setting of the correct combination of exposure factors is now effected by means of a comparison of brightness, which can be carried out exactly as a result of the great variation of luminous flux ensuing upon a small variation of voltage and as a result of the direct mutual adjoinment of the illuminated surfaces. If for example the surface 11 visible beside the picture area defining frame 16 appears brighter than the surface 12, then the set exposure factor combination corresponds to an under-exposure, in the converse case it corresponds to an over-exposure. The degree of incorrectness of exposure can be recognized by means of the contrast of brightness. The resistance attenuation elements 6, 7 are actuated for the setting of the correct exposure until the two surfaces ll, 12 appear equally bright.

in the present invention, in place of the incandescent lamps the lighting elements are formed as light source pillars the color of which are influenced by the frequency of their supply potential. for example electro luminescent plates, with which a comparison of both brightness and color is possible. In the case of the color equalization method a circuit arrangement of variable frequency generator 20 replaces the amplifier 10.

With the apparatus as described above, when a lens having a pre-selectable spring diaphragm is used, a bright measurement is possible, that is to say an exposure setting without darkening of the viewfinder image.

The surface 12 illuminated by the unregulated lighting element 1 serves not only as comparison surface for the correct exposure setting, but at the same time also to give information as to the voltage condition of the generator. It is advantageous to indicate when the generator voltage has reduced to a value at which exposure settings are no longer accurately indicated. The brightness of the unregulated lighting element indicates thevoltage condition. If the symbol which lies behind the section of the strip 14 having the least transparence for example the numeral 3 can be recognized, the voltage condition is good. If only the numerals 2 and 1 can be recognized, it is indicated that the generator output voltage is just still usable. If however only the numeral 1 can be recognized behind the most opaque part of the strip 14, the generator voltage is insufficient.

Yle claim:

. An exposure measuring apparatus including a first for adjusting the light emission of said second lighting element in accordance with required exposure factors when said source of supply potential is connected, wherein the lighting elements are formed as light source pillars the color of which are influenced by the frequency of their supply potential, e.g., electro luminescent plates, said source of supply potential is an alternating current source and said second lighting element is connected therewith via a variable frequency generator the frequency of which is influenced by the setting of said resistance attenuation element, said first and second lighting elements being arranged to illuminate respective surfaces positioned immediately adjacent one another whereby when the color and brightness of each of said surfaces is equal, the exposure factors are set to values required for accurate exposure. 

1. An exposure measuring apparatus including a first lighting element connectable to And influenced by a source of supply potential; means connected with said first lighting element for presetting the light emission of said first lighting element; a second lighting element; a photosensitive receiver connected in circuit with said second lighting element and connectable with said source of supply potential, said photosensitive receiver being responsive to prevailing light conditions for controlling the light emission of said second lighting element and at least one resistance attenuation element connected in circuit with said second lighting element for adjusting the light emission of said second lighting element in accordance with required exposure factors when said source of supply potential is connected, wherein the lighting elements are formed as light source pillars the color of which are influenced by the frequency of their supply potential, e.g., electro luminescent plates, said source of supply potential is an alternating current source and said second lighting element is connected therewith via a variable frequency generator the frequency of which is influenced by the setting of said resistance attenuation element, said first and second lighting elements being arranged to illuminate respective surfaces positioned immediately adjacent one another whereby when the color and brightness of each of said surfaces is equal, the exposure factors are set to values required for accurate exposure. 